It is well-known that a road finishing machine has a material conveyor system with which mixed laying material required for road construction is conveyed from a bunker located at the front in the direction of motion to the rear end of the road finishing machine in the direction of motion. For this, such a road finishing machine has a longitudinal conveyor system which is often designed as a scraper belt. In the process, the longitudinal conveyor system conveys the mixed material against the direction of motion from the front to the rear underneath the machine. The transverse conveyor system disposed at the rear end of the road finishing machine, which is often designed as spreading screw, is subsequently used to spread the mixed material in front of a screed and is to ensure the most constant and uniform distribution of the mixed material possible in the direction transverse to the road finishing machine. Such a road finishing machine is disclosed for example, in DE 93 08 170 U1.
It is furthermore known that the material throughput of the mixed material in the longitudinal conveyor system and in the transverse conveyor system depends on several parameters, for example the feed of the road finishing machine, the width of spread, the thickness of spread, and the density of the mixed material. For this reason, U.S. Pat. No. 3,678,817, EP 0 279 795 A2, DE 20 2004 004 082 U1, and DE 196 80 396 B4, for example, suggest systems for controlling the longitudinal and/or transverse conveyor system by open-loop or closed-loop control to adjust the material throughputs of the systems. These systems have in common that they have one or several sensors for detecting the current material throughput and regulate, on the basis of the data received from these sensors, the conveyor speeds or rates, respectively.
It is a disadvantage of the suggested systems that the cooperation of an open-loop or closed-loop control with the sensors for detecting the material throughput exhibits a certain inevitable latency, thus resulting in a delay between the event—namely a disadvantageous change of the material throughput—and the reaction to it. For example, when an extendable screed is employed and extended, the width of spread of the road finishing machine changes, so that an increased demand of mixed material suddenly arises in the region of the screed. The sensor or the sensors notice(s) this only with a certain delay in time, so that the connected open-loop or closed-loop control will try, as a reaction to this and with another increase in latency time, to compensate the increased demand for mixed material by increasing the conveyor rate of the longitudinal and/or the transverse conveyor system. The control is initially started sharply, so that a sudden acceleration of the drives of the material conveyor system occurs. By this, extreme load peaks can occur in the conveyor units or components, respectively, so that the diesel engine of the road finishing machine will get to its limits of performance. This can cause an engine stop as a protective function, and thus a laying stop of the road finishing machine. Such a behavior causes a disadvantageous quality of the road to be constructed and moreover has a disadvantageous effect on the laying speed.